Production Manual for Growers

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PRODUCTION MANUAL FOR GROWERS

Princettia®

Euphorbia hybrid, Family Euphorbiaceae

Princettia® is generally grown as Christmas flowering potted plant. It is treated as an annual, but is actually perennial by nature and will grow well outdoors under frost-free conditions.

Princettia® is a new interspecific hybrid of Euphorbia. Princettia® possesses some unique characteristics: it can be grown at lower temperatures than most poinsettias, it has a compact habit requiring no or little growth regulator application to control growth, has strong v-shaped branch structure which resists breakage, doesn’t require pinching to produce a branched plant, has a response time of 7 weeks and has some beautiful colours that are not available in normal poinsettias.

Growers with previous experience growing poinsettias will find Princettia® easier to grow than poinsettias. The production schedule is basically the same.

Pot rooted cuttings

Rooted cuttings should be potted within 2 days of receipt and the plug should be placed at the same level as the compost/media, avoiding stem contact with the soil. Maintain day temperature 70-75F (21-26C) and night temperature 70-75F (21-24C).

The growing media should have a pH of 5.8 – 6.3 with a starter EC of 1.5 – 2.0 mmhos/cm and high porosity.

Figure 3. Recently potted plants

Pot sizes will vary depending on the potting date and size of plant required, as Princettia® is very compact it is most suited to 10 -15cm pots. Fungal fly and white fly are two pests that can impact the crop at this stage. Check for wilting plants with fungal fly larvae in and around the roots – drench with an approved pesticide. White fly control at this stage is important as it is easier to contact the pests with spray application now than later in the crop when the canopy is more developed. From this stage, supply a general purpose liquid feed 2-3 times per week to promote maximum growth (e.g. 15:5:15).

Pinching (recommended, but optional)

The purpose of pinching is to promote lateral shoot development and uniformity. Pinching is performed 10 - 14 days after potting rooted cuttings. Decapitation of the apical meristem and associated leaves encourages axillary shoot growth from the remaining nodes. Pinching can be performed by hand or using a sharp knife, the plant must be turgid at the time to get a clean break. The timing of pinching depends on several factors including the desired number of nodes on the stem, the scheduled start date of short days, and root establishment.

For a 10cm (4inch) crop leave 4-5 nodes below the pinch to develop a finished plant with 4-5 flowering heads. A 15cm (6 inch) crop will need 6 – 8 nodes below the pinch to finish with 6-8 flowering heads. Higher node numbers may only be viable under special circumstances and are generally not recommended due to the increased space requirements.

Figure 4. Prior to Pinching

Figure 5. Pinched plant on left, unpinched on right

Start short-day phase for flower induction

From 10-14 days after pinching the plants will be ready for the induction of flowering. The plants should look like Figure 6 below.

Figure 6. Two weeks after Pinching

Floral induction is the first stage of flowering and begins 5-7 days after the critical day length is reached, in Europe it is September 21st and in Australia it is 21st March (<12 hours). Response time is the time from flower initiation to pollen shed or saleability, based on experience in Northern Europe, this period is from 7-8 weeks.

From initiation to bract expansion and the final stages of finishing, temperature should be maintained during the day at 70-75F (21-26C) and night at 65-68F (18-20C).

Light intensity during this phase should be ~1200 umol m-2 s-1. Maintain the average temperature during this phase at about 65-68F (18-20C). Warmer temperatures will speed growth. Plants can be spaced at this stage, or after a maximum of two weeks (wk 11). A good guide is to space when foliage begins to touch between adjacent plants.

Finish, saleable

Figure 7. Finished product in 15cm pot

Finished plants can be kept in the greenhouse for several weeks without losing quality provided the same conditions are maintained as during floral initiation and development. The plants will grow more bracts and develop fuller ‘heads’.

Please note that Princettia® cultivars are susceptible to some sporting. This is due to their unique mode of breeding. In particular the lighter pink cultivars will sometimes revert back to pink. The plants will nearly always grow the same as the rest of the crop but have a different bract colour. A small amount of sporting is normal for this crop.

Post-harvest

Finished plants should be carefully sleeved and packed. During packing and transport avoid bract abrasion as it can cause bruising of the bracts. Pink bracted varieties will show white marks where they have been damaged. Transport at temperatures >10C (50F) to avoid chilling injury and ensure the plants are un-sleeved for retail display. Avoid exposure to freezing temperatures or chilling winds. Keep the medium moist at all times, but not overwatered. No fertiliser is required at this stage.

Pest & Diseases

PESTS

Fungal Gnat (Bradysia spp.)

Are small slender, dark coloured flies that are about 3mm long with long legs and antennae. Their appearahce is similar to miniature mosquitoes. They thrive under benches and around moist soil. The larvae can invade plant tissue feeding on young roots, they can transmit fungal diseases to poinsettia.

Control methods are very good hygiene practices around the nursery and remove any lingering pockets of moisture on the greenhouse floor and contact your chemical supplier for up to date chemicals recommendations.

Whitefly

Are a common problem especially under a warm growing regime. Glasshouse whitefly (Trialeurodes vaporariorum) is the main strain, but lately Bemesia tabaci could be a major threat, tabaci is a transmitter of virus, this is the difference over common glasshouse whitefly.

Damage to the crop is obviously small fly’s visible and they will excrete honeydew in severe cases which causes discoloration of the foliage

Control of both types can be by chemicals or by Biological control agents. Contact your local adviser for up to date control methods.

Western Flower Thrips ( Frankliniella occidentalis)

Is rarely a problem as Princettia® is not a preferred host. Under high numbers in greenhouses where other suitable hosts are grown (such as plants from the Compositae family) damage can occur on Princettia. Damage is characterised by distorted foliage. Control can be by chemicals or by Biological control agents. Contact your local adviser for up to date control methods.

Aphids

Several types can feed on Princettia®. Control can be by chemicals or by Biological control agents. Contact your local adviser for up to date control methods.

Red Spider Mite (Tetranychus urticea)

Also called two spotted mite, but more commonly known in the UK as glasshouse red spider mite. Not normally a problem in shortening day length and temperature. A likely problem at the late stage of the crop but if grown cold it is unlikely to be seen. Control can be by chemicals or by Biological control agents. Contact your local adviser for up to date control methods.

DISEASES

Sanitation and the cleanliness of the growing environment are very important. The greenhouse environment must be clean and healthy at the start of the season. Remove all weeds and debris from the greenhouse, use only clean and new materials, pots, knives, etc. Hands, and benches must be disinfected.

Many diseases will occur where the environment is not ideal and the plants will come under excessive stress. Many fungi and bacteria will favour high relative humidity, therefore controlling the relative humidity is essential usually through the use of heating and venting. Avoid excess water on floors, especially during the evening to help reduce disease potential.

Botrytis cinerea (grey mold)

A common problem in all stages of the crop, in severe cases spores are clearly visible and can lead to plant death usually via attacking the stem. Most at risk are flowering plants ready for sale as the fungus can attack the flowers and anthers causing the flowers to abscise, affecting saleability. Chemical controls are easily available, but environmental conditions within the greenhouse can ensure this problem is kept to a minimum. Keep relative humidity below 85% by good air movement and appropriate temperature management. Water the plants in the morning, space plants as required.

Pythium root rot (Phythium spp.)

A fungal disease which begins as a brown root rot and then can progress up the stem, a brown or black canker may form on the soil line. Usually occurs during propagation. Hygiene should be reviewed if this disease is prevalent.

Rhizoctonia (Rhizoctonia solani)

This disease commonly occurs during propagation. It begins with reddish brown lesions on the stem near the soil line, the disease will progress up the stem as well as down in to the roots. On mature plants a brown-black canker begins at or below the soil line.

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31/08/2016